fix(engine): do not create another cache for multiproof task

[shekhirin]

Problem

Every time cache_for is called, we check that it's going to be the only cache in use:

reth/crates/engine/tree/src/tree/payload_processor/mod.rs

Lines 786 to 788 in 790a73c

	// Check `is_available()` to ensure no other tasks (e.g., prewarming) currently hold
	// a reference to this cache. We can only reuse it when we have exclusive access.
	.filter(|c| c.executed_block_hash() == parent_hash && c.is_available())

First cache_for call is happening here

reth/crates/engine/tree/src/tree/payload_processor/mod.rs

Line 252 in fa05d19

self.spawn_caching_with(

Second is here

reth/crates/engine/tree/src/tree/payload_processor/mod.rs

Line 297 in fa05d19

let saved_cache = self.cache_for(parent_hash);

Which leads to always creating a new cache on the second call

Solution

Get cache once with cache_for and pass to all consumers.